For instance in paper, board and pulp industry a need has arisen to carry out measurements of stock for supervising and controlling the process. Stock refers to suspension that includes liquid, particles of a solid such as fibres and possibly sticks and some gas. The idea of the measurements is to determine the properties of wood fibres to be used for making paper or board, such as length, thickness or the fibre wall thickness or other stock properties, such as freeness.
Generally the sample taken from the process is to be diluted in order to analyze it. A sample that is too consistent may cause a measuring device or an analyzer to clog up. A sample that is too consistent may also cause for instance a measurement error, if an excessive amount of individual objects, such as fibres or sticks, simultaneously fall on the observation area of the measuring device. The aim is to measure frequently from the same sample various properties of the stock or of a component thereof. Typically the different measurements are carried out for different consistencies that appropriately suit each measurement.
Typically a sample is directed from a sampler to a sample processing system, into which dilution water is conveyed. The diluted sample can be circulated in the system, which may comprise for instance a sampling vessel and/or a sampling tube system, in order to ensure the homogeneity of the sample by means of for instance a pump or a mixer. As regards the measurement quality it is generally important that an adequate amount of the undiluted sample or a component thereof is taken for analysis. The result of a minimum amount requirement of a representative sample and the dilution need of the sample is often that the sample processing system to be dimensioned in accordance with the amount of diluted sample becomes large and expensive. The use of excessive dilution liquid also increases the costs and also the environmental load. Owing to the “slowness” caused by the size and structure of the sample processing and dilution system the flow of the dilution liquid in relation to the amount of sample generally has to be kept small. This may significantly prolong the total time required for analyzing the sample.